Thermoform windshield stack with integrated formable mold and method

ABSTRACT

A method of installing a stack of two or more lenses on a curved substrate includes placing a moldable covering on a curved substrate, the moldable covering including a stack of two or more lenses, an adhesive layer interposed between each pair of adjacent lenses from among the two or more lenses, and a sacrificial layer disposed on an outermost lens of the stack, the sacrificial layer including a sacrificial lens and a sacrificial adhesive interposed between the sacrificial lens and the outermost lens of the stack. The method may include applying heat and pressure to the sacrificial layer and peeling off the sacrificial layer to reveal the stack of two or more lenses.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 16/778,928, filed Jan. 31, 2020, which relates to and claims the benefit of U.S. Provisional Application No. 62/799,880, filed Feb. 1, 2019 and entitled “Thermoform Windshield Stack With Integrated Formable Mold,” the entire contents of which is expressly incorporated herein by reference.

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND 1. Technical Field

The present disclosure relates generally to transparent coverings for windows and, more particularly, to transparent coverings having multiple lenses stacked one over the other and adhered together by adhesive.

2. Related Art

There may be various advantages to affixing transparent lenses to curved substrates such as windshields (also referred to as windscreens). Such coverings may provide protection from pitting and cracking, tinting (e.g. for privacy), thermal insulation, blocking of ultraviolet (UV) radiation, and/or decoration. A stack of such transparent lenses may allow for easy tear-away as the outermost lens becomes dirty and obstructs the driver's vision, such as might occur in vehicles for off-road use.

While the surface of a typical windshield usually exhibits a compound curvature, the transparent lenses may themselves be flat, such as in the case of polyethylene terephthalate (PET) films manufactured in a roll-to-roll process. In order to install a flat film to a compound curved windshield surface, the film may be drape formed over the windshield, e.g. by laying the film over the windshield and applying heat to the uppermost surface to shrink or stretch the film to take the shape of the windshield. However, this process may result in uneven heating or overheating, which may cause optical distortion in the film and may result in areas where the film is not adequately adhered to the windshield. In addition, the efforts of the installer to apply pressure to the film with a card or squeegee may result in permanently scratching the visible surface during installation.

BRIEF SUMMARY

The present disclosure contemplates various systems and methods for overcoming the above drawbacks accompanying the related art. One aspect of the embodiments of the present disclosure is a method of installing a stack of two or more lenses on a curved substrate. The method may include placing a moldable covering on a curved substrate, the moldable covering including a stack of two or more lenses, an adhesive layer interposed between each pair of adjacent lenses from among the two or more lenses, and a sacrificial layer disposed on an outermost lens of the stack, the sacrificial layer including a sacrificial lens and a sacrificial adhesive interposed between the sacrificial lens and the outermost lens of the stack. The method may include applying heat and pressure to the sacrificial layer and peeling off the sacrificial layer to reveal the stack of two or more lenses.

The curved substrate may be a compound curved substrate. The curved substrate may be a windshield.

The sacrificial layer may be more heat resistant than the outermost lens of the stack.

The sacrificial layer may be less scratch resistant than the outermost lens of the stack.

The sacrificial lens may comprise a biaxially oriented polyethylene terephthalate film. The biaxially oriented polyethylene terephthalate film may be able to withstand temperatures between room temperature and 220° C. for two hours.

The sacrificial lens may comprise an opaque polyester film. The outermost lens of the stack may comprise a transparent polyethylene terephthalate film.

Another aspect of the embodiments of the present disclosure is a moldable covering affixable to a curved substrate, the moldable covering may include a stack of two or more lenses, an adhesive layer interposed between each pair of adjacent lenses from among the two or more lenses, and a sacrificial layer disposed on an outermost lens of the stack, the sacrificial layer including a sacrificial lens and a sacrificial adhesive interposed between the sacrificial lens and the outermost lens of the stack, the sacrificial layer being more heat resistant than the outermost lens of the stack.

The sacrificial lens may comprise a biaxially oriented polyethylene terephthalate film. The biaxially oriented polyethylene terephthalate film may be able to withstand temperatures between room temperature and 220° C. for two hours.

The sacrificial lens may comprise an opaque polyester film. The outermost lens of the stack may comprise a transparent polyethylene terephthalate film.

Another aspect of the embodiments of the present disclosure is a moldable covering affixable to a curved substrate. The moldable covering may include a stack of two or more lenses, an adhesive layer interposed between each pair of adjacent lenses from among the two or more lenses, and a sacrificial layer disposed on an outermost lens of the stack, the sacrificial layer including a sacrificial lens and a sacrificial adhesive interposed between the sacrificial lens and the outermost lens of the stack, the sacrificial layer being less scratch resistant than the outermost lens of the stack.

The sacrificial lens may comprise a biaxially oriented polyethylene terephthalate film. The biaxially oriented polyethylene terephthalate film may be able to withstand temperatures between room temperature and 220° C. for two hours.

The sacrificial lens may comprise an opaque polyester film. The outermost lens of the stack may comprise a transparent polyethylene terephthalate film.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which:

FIG. 1 is schematic side view of a moldable covering according to an embodiment of the present disclosure;

FIG. 2 shows the moldable covering placed on a windshield at the beginning of a process of applying heat and pressure to a sacrificial layer of the moldable covering;

FIG. 3 shows the moldable covering on the windshield at the end of the process of applying heat and pressure;

FIG. 4 shows the moldable covering on the windshield as the sacrificial layer is being peeled off to reveal a stack of transparent lenses;

FIG. 5 shows the stack of transparent lenses after they have been trimmed to fit the windshield; and

FIG. 6 shows an example operational flow according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

The present disclosure encompasses various embodiments of a moldable covering including a stack of two or more lenses and an installation method thereof. The detailed description set forth below in connection with the appended drawings is intended as a description of several currently contemplated embodiments and is not intended to represent the only form in which the disclosed invention may be developed or utilized. The description sets forth the functions and features in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions may be accomplished by different embodiments that are also intended to be encompassed within the scope of the present disclosure. It is further understood that relational terms such as first and second and the like are used solely to distinguish one from another entity without necessarily requiring or implying any actual such relationship in order between such entities.

FIG. 1 is schematic side view of a moldable covering 100 according to an embodiment of the present disclosure. The moldable covering 100 may be affixed to a curved substrate 10 such as a windshield as part of the process of installing a stack of lenses 110 a, 110 b, 110 n (collectively lenses 110). The installed stack of lenses 110 may provide the substrate 10 with protection, tinting, thermal insulation, blocking ultraviolet (UV) radiation, decoration, and/or the ability to peel away and discard the outermost layer 110 n (and thereafter any newly revealed layers 110) as needed during the lifetime of the product. In addition to the lenses 110, the moldable covering 100 may include adhesive layers 120 a, 120 b, . . . 120 n (collectively adhesive layers 120) provided respectively on each lens 110, such that an adhesive layer 120 is interposed between each pair of adjacent lenses 110 of the stack. On the outermost lens 110 n of the stack of lenses 110, a sacrificial layer 130 may be provided to allow for an improved process of installing the stack of lenses 110 to the substrate 10. The sacrificial layer 130 may include a sacrificial lens 132 and a sacrificial adhesive 134 interposed between the sacrificial lens 132 and the outermost lens 110 n of the stack of lenses 110. When installing the stack of lenses 110, heat and pressure may be applied to the sacrificial layer 130 to conform the stack of lenses 110 to the shape of the curved substrate 10. Thereafter, the sacrificial layer 130 may be peeled away to reveal the final product 140 including the installed lenses 110.

If one were to only drape form the stack of lenses 110 on the curved substrate 10 without the sacrificial layer 130, the process could result in uneven heating or overheating as explained above, as well as the possibility of permanently scratching the outermost lens 110 n with a card or squeegee. The inventor has found that these difficulties stem largely from the lack of a female mold cavity to apply pressure as the stack of lenses 110 conforms to the male surface represented by the curved substrate 10. As a result, neither heat nor pressure is evenly distributed when the installer attempts to mold the stack of lenses 110 to the curved substrate 10, resulting in the stated difficulties. By providing the sacrificial layer 130 to serve as the missing female mold cavity, the disclosed moldable covering 100 may overcome these deficiencies in at least two ways. First, the sacrificial layer 130 may allow the installer to apply heat and pressure without fear of scratching or otherwise damaging the end product. The sacrificial layer 130 may simply be discarded along with any surface damage, while the underlying outermost lens 110 n of the stack of lenses 110 remains unblemished. Second, as heat and pressure are applied to the stack of lenses 110 through the intervening sacrificial layer 130, the sacrificial layer 130 may serve to distribute the heat and pressure over a wider area, resulting in a more even application of heat and pressure as the sacrificial layer 130 and underlying stack of lenses 110 together conform to the shape of the curved substrate 10.

The lenses 110 may comprise a transparent polyethylene terephthalate (PET) film such as a biaxially-oriented polyethylene terephthalate (BoPET) and may be fabricated from sheets of polyester film sold under the registered trademark Mylar owned by the DuPont Company. The thickness of each lens 110 may be between 0.5 mil and 7 mil (1 mil is 0.001″), for example, 2 mil. Even after the adhesive material of the adhesive layers 120 is applied to a 2-mil thickness lens 110, the combined thickness of the 2-mil thickness lens 110 and adhesive layer 120 may still be 2 mil due to the adhesive layer 120 having only a nominal thickness.

The adhesive used in the adhesive layers 120 may be applied, for example, in selective areas around the periphery of the moldable covering 100 as described in U.S. Pat. No. 6,536,045 to Wilson, issued Mar. 25, 2003 and entitled “Tear-off Optical Stack Having Peripheral Seal Mount,” the entire contents of which is expressly incorporated herein by reference. The adhesive layers 120 may be made of a clear optical low tack material and may comprise a water-based acrylic optically clear adhesive or an oil-based clear adhesive. The adhesive layer 120 a used to affix the moldable covering 100 to the substrate 10 may be the same as or different from (e.g. stronger than) that of the adhesive layers 120 b, . . . 120 n interposed between each pair of adjacent lenses 110 of the stack. A stronger adhesive may be used, for example, in a case where individual lenses 110 are to be torn off without removing the entire stack of lenses 110 from the substrate 10 during use. Along the same lines, the adhesive used for the adhesive layers 120 b, . . . 120 n interposed between each pair of adjacent lenses 110 may be stronger than the sacrificial adhesive 134 of the sacrificial layer 130, such that the sacrificial layer 130 may be torn off without removing the outermost lens 110 n from the stack of lenses 110. The sacrificial adhesive 134 may similarly be a low tack material and may comprise a water-based acrylic optically clear adhesive or an oil-based clear adhesive. However, in the case of the sacrificial adhesive 134, an opaque adhesive may be used instead since the sacrificial adhesive 134 is removed in the final product 140.

The lenses 110 may be optimized for scratch resistance and/or blocking (absorbing or reflecting) UV radiation. For example, an exterior side of each lens 110 may be deposited, sprayed, laminated, or otherwise coated with a coating (e.g. silicon ester acrylate oligomer and/or acrylated urethane polyol) that is optimized for scratch resistance and/or blocking UV radiation as desired for properties suitable to the finished product 140. These properties may be relaxed in the fabrication of the sacrificial layer 130, since the sacrificial layer 130 will not be present after the installation is complete. Thus, for example, the sacrificial layer 130 may be less scratch resistant than the outermost lens 120 n of the stack of lenses 120. Meanwhile, the sacrificial layer 130 may be optimized for heat resistance, for example, coated with a coating (e.g. silicon ester acrylate oligomer and/or acrylated urethane polyol) that is optimized for heat resistance, since the sacrificial layer 130 may be heated directly as part of thermoforming the moldable covering 100 to the shape of the curved substrate 10. Such heat resistance properties may be relaxed in the underlying stack of lenses 100 as these lenses may only be subjected to the heat indirectly through the sacrificial layer 130. Thus, for example, the sacrificial layer 130 may be more heat resistant than the outermost lens 110 n of the stack of lenses 100.

The sacrificial layer 130 may be made of a high temperature PET, for example, one that is able to withstand temperatures between room temperature and 220° C. for two hours (e.g. without deteriorating). The high temperature PET may be a clear BoPET, allowing for observation of the underlying stack of lenses 110 during the molding process, and may, for example, be a polyester film sold under the tradename Hostaphan RBB by the Mitsubishi Polyester Film Group. Such a high temperature BoPET may be preferred when using hot air to heat the sacrificial layer 130 during the molding process. Alternatively, the sacrificial layer 130 may be made of an opaque (e.g. white) polyester film such as one sold under the tradename Hostaphan WIN by the Mitsubishi Polyester Film Group. Such an opaque polyester film may provide increased thermal uniformity when using infrared heaters to heat the sacrificial layer 130 during the molding process.

While the sacrificial layer 130 (e.g. the sacrificial lens 132 and/or the sacrificial adhesive 134) may be optimized to withstand the heat of the installation process and to evenly distribute heat and pressure to the underlying stack of lenses 110, it is generally unnecessary for the sacrificial layer 130 to meet the more stringent performance standards of the underlying stack of lenses 110. For example, the stack of lenses may be designed to meet federal standards for visible light transmission (e.g. 70%), such as may be set forth in the American National Standards Institute (ANSI) standards Z26.1-1966 and Z26.1a-1969, as well as to resist scratching (e.g. by windshield wipers) as described above and/or to absorb or reflect UV light to protect the lenses 110 from sun damage. By relaxing these requirements in the sacrificial layer 130, while at the same time providing a more robust surface for applying heat and pressure without worry during installation, the moldable covering 100 may allow for a more efficient method of installing the stack of lenses 110. With the sacrificial layer 130 acting as a female mold cavity, the layers of lenses 110 and adhesive 120 are held, form, and cure better to the curved substrate 10 and never get scratched during the installation process.

FIG. 2 shows the moldable covering 100 placed on a windshield of a car 20, the windshield serving as the substrate 10, at the beginning of a process of applying heat and pressure to the sacrificial layer 130 of the moldable covering 100. The moldable covering 100 may be adhered to the windshield by a dry mount adhesive 120 a (see FIG. 1 ) as disclosed, for example, in U.S. Pat. No. 9,295,297 to Wilson, issued Mar. 29, 2016 and entitled “Adhesive Mountable Stack of Removable Layers,” the entire contents of which is expressly incorporated herein by reference. Alternatively, a wet mount adhesive 120 a may be used as disclosed, for example, in U.S. Pat. No. 9,128,545 to Wilson, issued Sep. 8, 2015 and entitled “Touch Screen Shield,” the entire contents of which is expressly incorporated herein by reference. Since the moldable covering 100 may be flat (e.g. having been manufactured in a roll-to-roll process), the moldable covering 100 may not initially conform to the curved shape of the windshield, resulting in regions of greater or less adhesion and pockets/bubbles of air between the moldable covering 100 and the windshield. Therefore, in order to conform the moldable covering 100 to the shape of the windshield, heat and pressure may be applied using a heater 30 such as a hot air source (e.g. a heat gun or blow dryer) or an infrared heater. At the same time, pressure may be applied to the moldable covering 100 using a card or squeegee. As the installer heats and presses down on the sacrificial layer 130 of the moldable covering 100, the sacrificial layer 130 may shrink and stretch to take on the contour of the opposing curved substrate 10 (the windshield) with the stack of lenses 110 therebetween. In this way, the sacrificial layer 130 may act as a female mold cavity to thermoform the underlying stack of lenses 110 to the shape of the windshield, evenly distributing the heat and pressure to shrink and stretch the lenses 110 to the correct shape and cure the adhesive layers 120.

FIG. 3 shows the moldable covering 100 on the windshield at the end of the process of applying heat and pressure. At this stage, the moldable covering 100, including the sacrificial layer 130 as well as the underlying lenses 110, is molded to the curved shape of the windshield without air pockets/bubbles. The upper surface of the sacrificial layer 130 may have various scratches and other blemishes caused by the installer as the installer applied pressure to the moldable covering 100 using a squeegee or card. However, the underlying lenses 110 have been protected by the sacrificial layer 130 and are thus untouched.

FIG. 4 shows the moldable covering 100 on the windshield as the sacrificial layer 130 is being peeled off to reveal the stack of transparent lenses 110. Remaining on the windshield is the final product 140 (see FIG. 1 ) including the stack of lenses 110 and adhesive layers 120. The final product 140 may meet performance standards as described above, including federal standards for visible light transmission (e.g. 70%), as well as scratch resistance and/or UV absorption or rejection. The lenses 110 of the final product 140 may be accurately conformed to the shape of the windshield and may be free of blemishes, even on the outermost lens 110 n. The peeled off sacrificial layer 130 may simply be discarded.

FIG. 5 shows the final product 140 including the stack of transparent lenses 110 after the stack of transparent lenses 110 has been trimmed to fit the windshield serving as the substrate 10. The stack of transparent lenses 110 may be trimmed using a knife such as a utility knife or box cutter with a stainless-steel blade (a carbon blade may damage the windshield). The trimming may be done after the sacrificial layer 130 has been removed from the moldable covering 100 as shown in FIG. 5 , such that only the revealed final product 140 is trimmed. Alternatively, the trimming may be done prior to the removal of the sacrificial layer 130, once the moldable covering 100 has been conformed to the shape of the windshield as shown in FIG. 3 . In either case, the resulting trimmed final product 140 may effectively be invisible as it matches the shape of the windshield beneath (though it may alter the coloring of the windshield as in the case of window tinting).

FIG. 6 shows an example operational flow according to an embodiment of the present disclosure. The operational flow of FIG. 6 may serve as an example method of installing the final product 140 including the stack of lenses 110 shown in FIG. 1 . First, the moldable covering 100, including both the final product 140 and the sacrificial layer 130, may be placed on a curved substrate 10 such as the windshield of the car 20 shown in FIG. 2 (step 610), with the adhesive layer 120 a on the windshield and the sacrificial layer 130 facing outward away from the windshield. For easier installation, the moldable covering 100 may be rough cut (e.g. using an electric film cutter) so as not to extend too far outside the windshield. The operational flow may continue with applying heat and pressure to the sacrificial layer 130 of the moldable covering 100 as described in relation to FIGS. 2 and 3 in order to thermoform the moldable covering 100 to the curved shape of the windshield (step 620). After allowing the moldable covering 100 to cool down, the operational flow may conclude with peeling off the sacrificial layer 130 to reveal the final product 140 as described in relation to FIG. 4 (step 630) and performing a final trim as described in relation to FIG. 5 (step 640). As noted above, steps 630 and 640 may be performed in the order shown in FIG. 6 or in reverse order. The final product 140 including the stack of lenses 110 is now uniformly formed and affixed to the windshield surface.

In the example of FIG. 1 , three lenses 110 are shown. However, it is contemplated for the moldable covering 100 to include a stack of four or more lenses 110, or a stack of two lenses 110 or even a single lens 110, with the number of lenses 110 depending on the particular application. Counterintuitively, the inventor has found that a stack of multiple lenses 110 is easier to thermoform to a curved substrate 10 than a stack having a single lens 110.

Throughout this disclosure, the word “transparent” is used broadly to encompass any materials that can be seen through. The word “transparent” is not intended to exclude translucent, hazy, frosted, colored, or tinted materials.

The coatings described throughout this disclosure may be applied according to known methods such as spin coating, dip coating, or vacuum deposition.

The above description is given by way of example, and not limitation. Given the above disclosure, one skilled in the art could devise variations that are within the scope and spirit of the invention disclosed herein. Further, the various features of the embodiments disclosed herein can be used alone, or in varying combinations with each other and are not intended to be limited to the specific combination described herein. Thus, the scope of the claims is not to be limited by the illustrated embodiments. 

What is claimed is:
 1. A method of installing a stack of two or more lenses on a curved substrate, the method comprising: placing a moldable covering on a curved substrate, the moldable covering including a stack of two or more lenses, an adhesive layer interposed between each pair of adjacent lenses from among the two or more lenses, and a sacrificial layer disposed on an outermost lens of the stack, the sacrificial layer including a sacrificial lens and a sacrificial adhesive interposed between the sacrificial lens and the outermost lens of the stack; applying heat and pressure to the sacrificial layer; and peeling off the sacrificial layer to reveal the stack of two or more lenses.
 2. The method of claim 1, wherein the curved substrate is a compound curved substrate.
 3. The method of claim 2, wherein the curved substrate is a windshield.
 4. The method of claim 1, wherein the sacrificial layer is more heat resistant than the outermost lens of the stack.
 5. The method of claim 4, wherein the sacrificial layer is less scratch resistant than the outermost lens of the stack.
 6. The method of claim 1, wherein the sacrificial layer is less scratch resistant than the outermost lens of the stack.
 7. The method of claim 1, wherein the sacrificial lens comprises a biaxially oriented polyethylene terephthalate film.
 8. The method of claim 7, wherein the biaxially oriented polyethylene terephthalate film can withstand temperatures between room temperature and 220° C. for two hours.
 9. The method of claim 1, wherein the sacrificial lens comprises an opaque polyester film.
 10. The method of claim 9, wherein the outermost lens of the stack comprises a transparent polyethylene terephthalate film. 